Ubuntu server is very good, but you really will have to deep-dive into Apache and the mail server of your choice which adds about 200% over just learning Linux. In your case, though, it sounds more like you are setting up to serve a few PHP apps. If that is the case, I'd recommend setting up on a Cpanel based hosting service (Cpanel runs on CentOS and has become a de-facto standard for serving PHP apps like PHPBB 3). If you need a dedicated server, you can find places where you can get a Cpanel server for $100/month-$200/month... or you can license it for your own server. There is a reason that Cpanel is so popular...
Ignore all the static here about "another admin who doesn't know what he/she is doing". Every one of us here knew nothing at one time. Yes, you'll learn a few lessons the hard way, but as long as you have regular backups and pay attention to ensuring users have strong passwords, you probably will not do anything you can't recover from.